AMWA To Extend MXF for Contribution

The Advanced Media Workflow Association (AMWA) is developing a version of the file specification MXF for Contribution (or AS-11) to meet the broader needs of North American and European broadcasters. The all-industry coalition of broadcasters and equipment vendors said it has been taking the pain out of interoperability and universal file exchange by creating constrained versions of MXF that vendors can use to facilitate interoperability between equipment in the program chain.

Brad Gilmer, Executive Director of the AMWA, said that as videotape moves towards end of life, broadcasters are looking to define workable file delivery specifications to facilitate the receipt of content from program makers.

"Broadcasters are finding that file exchange is beset with pitfalls; that was not the case with videotape," said Gilmer. "The AMWA MXF for Contribution, AS-11, constrains MXF for this use case. The fewer variables, the easier it is for vendor to supply compliant equipment to support file exchange across the broadcast production chain."

The AMWA has already released the AS-03 specification defining a format for ready-to-air material, but it said broadcasters still need a specification for a broadcast master file that can be used to prepare the transmission copies.

These issues led the main broadcasters in the UK to form the Digital Production Partnership (DPP), with one of its aims to create a standard specification for file delivery from post-production to the broadcaster. Working with the AMWA, this led to MXF for Contribution Application Specification (AS-11). This defines a constrained MXF file and details video and audio codecs along with necessary metadata. AS-11 files can be edited for breaks, retimed, and may have additional language tracks, captions and subtitles wrapped into the file container.

The proposed update to AS-11 will extend the specification to better match use cases beyond those of the UK's DPP. In North America, CBC, PBS and Turner Broadcasting have expressed interest in the project. Interest is growing in Europe as well.

The UK development of AS-11 was based on the AVC-Intra codec, but other broadcasters favor the HDCAM 50Mb/s 422 long GOP codec, along with the edit codecs, Avid DNxHD and Apple ProRes so the codec set will be extended.

The project to extend AS-11 looks to combine future requirements into the next release of the specification, and the AMWA is now collecting use cases for MXF file delivery and encourages interested parties to participate.

The original AS-11 has a basic metadata set, plus a DPP specific "shim". A shim allows a user to further constrain the specification by adding house metadata, further limiting codecs to specific bit rates or line and frame rates or defining other such parameters. In an extended AS-11, each broadcaster will constrain the specification with their own shim, as the DPP does today.